Ancillary (or spectator) ligand-metal coordination complexes (e.g., organometallic complexes) and compositions are useful as catalysts, additives, stoichiometric reagents, monomers, solid state precursors, therapeutic reagents and drugs. Ancillary ligand-metal coordination complexes of this type can be prepared by combining an ancillary ligand with a suitable metal compound or metal precursor in a suitable solvent at a suitable temperature. The ancillary ligand contains functional groups that bind to the metal center(s), remain associated with the metal center(s), and therefore provide an opportunity to modify the steric, electronic and chemical properties of the active metal center(s) of the complex.
Certain known ancillary ligand-metal complexes and compositions are catalysts for reactions such as oxidation, reduction hydrogenation, hydrosilylation, hydrocyanation, hydroformylation, polymerization, carbonylation, isomerization, metathesis, carbon-hydrogen activation, carbon-halogen activation, cross-coupling, Friedel-Crafts acylation and alkylation, hydration, dimerization, trimerization, oligomerization, Diels-Alder reactions and other transformations.
One example of the use of these types of ancillary ligand-metal complexes and compositions is in the field of polymerization catalysis. In connection with single site catalysis, the ancillary ligand typically offers opportunities to modify the electronic and/or steric environment surrounding an active metal center. This allows the ancillary ligand to assist in the creation of possibly different polymers. Group 4 metallocene based single site catalysts are generally known for polymerization reactions. See, generally, “Chemistry of Cationic Dicyclopentadienyl Group 4 Metal-Alkyl Complexes”, Jordan, Adv. Organometallic Chem., 1991, Vol. 32, pp. 325–153 and “Stereospecific Olefin Polymerization with Chiral Metallocene Catalysts”, Brintzinger, et al., Angew. Chem. Int. Ed. Engl., 1995, Vol. 34, pp. 1143–1170, and the references therein, all of which is incorporated herein by reference.
However, those of skill in the art of single site catalysis appreciate that there may be substantial differences in performance between different metal centers. For example, U.S. Pat. No. 5,064,802 discloses a broad category of mono-cyclopentadienyl ligand catalysts with a broad disclosure of useful metals, and U.S. Pat. No. 5,631,391 more specifically discloses that titanium metal centers offer performance advantages with respect to the same or similar ligands. Additionally, Coates, et al., Angew. Chem. Int. Ed., 2000, vol. 39, pp. 3626–3629 describes the unpredictable nature of olefin polymerization catalyst structure-activity relationships. Thus, references that describe, for example, groups 3–13 and the lanthanides, for example in U.S. Pat. No. 6,103,657, are not of adequate performance indicators of all that is within the scope of what is allegedly described. Moreover, as those of skill in the art appreciate, differences in ligand substituents typically polymerize different monomers at different performances under different polymerization conditions, and discovering those specifics remains a challenge.
One application for metallocene catalysts is producing isotactic polypropylene. An extensive body of scientific literature examines catalyst structures, mechanism and polymers prepared by metallocene catalysts. See, e.g., Resconi et al., “Selectivity in Propene Polymerization with Metallocene Catalysts,” Chem. Rev. 2000, 100, 1253–1345 and G. W. Coates, “Precise Control of Polyolefin Stereochemistry Using Single-Site Metal Catalysts,” Chem. Rev. 2000, 100, 1223–1252 and the references sited in these review articles. See also, U.S. Pat. No. 5,026,798 that reports a mono-cyclopentadienyl metallocene for the production of isotactic polypropylene. Isotactic polypropylene has historically been produced with heterogeneous catalysts that may be described as a catalyst on a solid support (e.g., titanium tetrachloride and aluminum alkyls on magnesium dichloride). This process typically uses hydrogen to control the molecular weight and electron-donor compounds to control the isotacticity. See also EP 0622380, U.S. Pat. No. 4,297,465, U.S. Pat. No. 5,385,993 and U.S. Pat. No. 6,239,236.
Given the extensive research activities with respect to metallocene catalysts, there is continued interested in the next generation of non-cyclopentadienyl ligands for olefin polymerization catalysts providing attractive alternatives. See, e.g., “The Search for New-Generation Olefin Polymerization Catalysts: Life beyond Metallocenes”, Gibson, et al., Angew. Chem. Int. Ed., 1999, vol. 38, pp. 428–447; Organometallics 1999, 18, pp. 3649–3670. Recently, such systems have been discovered, see, e.g., U.S. Pat. No. 6,103,657 and U.S. Pat. No. 5,637,660. For isotactic polypropylene, bis-amide catalysts have been disclosed in U.S. Pat. No. 5,318,935 and amidinate catalysts have been disclosed in WO 99/05186. See also U.S. Pat. No. 6,214,939.
There remains a need for the discovery and optimization of non-cyclopentadienyl based catalysts for olefin polymerization, and in particular for certain polymers, such as isotactic polypropylene and ethylene-□-olefin copolymers. For a solution polymerization methodology, this need may be acute in view of the lack of versatile catalysts for the preparation of isotactic polypropylene at commercially acceptable temperatures. Indeed, new polymer properties are disclosed herein for isotactic polypropylene, ethylene-styrene copolymers and ethylene-isobutylene copolymers.